Resin composition, resin cured product, and liquid discharge head

ABSTRACT

An epoxy resin composition, including: an epoxy resin (A) represented by Formula (1); an epoxy resin (B) having an epoxy equivalent of 220 or less and having twice or more epoxy groups in a molecule than epoxy groups of the epoxy resin (A); and a photocationic polymerization initiator (C), in which: the epoxy resins (A) and (B) constitute main components; and a weight of the epoxy resin (A) is 40% or more and a weight of the epoxy resin (B) is 30% or more with respect to a total weight of the epoxy resins (A) and (B): 
                         
where: R represents a hydrogen atom, a methyl group, an ethyl group, a propyl group, or a t-butyl group; n represents an integer of 0 or more and 4 or less; and m represents an integer of 1 or more and 3 or less.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a resin composition, a resin curedproduct and a liquid discharge head.

2. Related Background Art

An epoxy resin composition is capable of providing a cured producthaving excellent heat resistance, adhesiveness, electrical insulatingproperties, and the like, and thus is preferably used in applicationssuch as a semiconductor sealer, a printed wiring board, paint, and acasting material. Of those, in electrical and electronic applicationsrequiring particularly high reliability, use of an epoxy resin(hereinafter, referred to as an epoxy resin (A)) represented by Formula(1) described below and having a dicyclopentadiene skeleton is proposed.The epoxy resin (A) has a bulky cyclic aliphatic hydrocarbon skeleton ina molecule and thus has properties of low water absorption property andlow dielectric constant:

where: R represents a hydrogen atom, a methyl group, an ethyl group, apropyl group, or a t-butyl group; n represents an integer of 0 to 4; andm represents an integer of 1 to 3.

Meanwhile, a photocuring technique involving cationic ring openingpolymerization of an epoxy resin with a cationic UV-curable initiator(photocationic polymerization initiator) is in practical use in wideranging fields such as coating agent, ink, a resist for producing asemiconductor, and a stereo lithography resin.

In recent years, there is known a method of producing a liquid dischargehead for forming a liquid passage by applying the photocuring techniqueand subjecting a photocationic curable resin layer laminated on asubstrate to photolithography techniques such as exposure anddevelopment. For example, Japanese Patent Application Laid-Open No.H03-184868 discloses a method of forming a liquid passage by subjectingan epoxy resin having a bisphenol-A, F, or S skeleton or an o-cresolnovolac-type epoxy resin to photocationic polymerization.

A known application example of the liquid discharge head is an ink jetrecording head in which the head is loaded in a recording device. Atpresent, a commercially available ink jet recording head has a high inkjet port density of 600 dpi and requires a technique of producing a fineink passage.

Therefore, the method of forming a passage for an ink jet recording headapplying photolithography techniques and described above is better thanconventionally known methods employing plating and laser processing inview of precision in forming a desired passage and discharge portpattern.

Meanwhile, a passage wall forming member of an ink jet recording head isconstantly in contact with ink during use of a product. Generally usedink is often alkaline and contains an organic solvent. Low waterabsorption property and excellent solvent resistance are stronglydesired for the passage wall forming member constantly in contact withsuch a substance. In the case where the passage wall forming member hasno such properties, the passage wall forming member undergoes volumeswelling and the passage or the discharge port deforms. Thus, a desireddischarge state may not be obtained, and the passage wall forming membermay peel off from the substrate.

SUMMARY OF THE INVENTION

The inventors of the present invention have studied forming a finepattern on an epoxy resin (A) having excellent properties of lowabsorption property as described above through photolithography, andapplying the fine pattern to a passage wall forming member of an ink jetrecording head.

As described below, the inventors of the present invention have formed apattern by dissolving an epoxy resin (A) containing a photocationicpolymerization initiator added in a solvent, forming an applied film ona substrate, and conducting exposure and development, and have evaluateda cured product obtained through curing.

As a result, the obtained cured product had sufficient properties from aviewpoint of low absorption property applicable to a current environmentemploying the cured product as an ink jet recording head, that is, anenvironment in which the cured product is in contact with ink for a longperiod of time.

However, no precise pattern satisfying properties currently required forthe passage wall forming member of the ink jet recording head wasobtained. To be specific, for pattern formation on the epoxy resin (A)through photolithography, pattern formation was conducted with anexposure providing desired pattern dimensions, and a pattern edge partbecame blunt. Further, in pattern formation with an exposure suppressingblunting of the pattern edge part, partial peeling of the resin wascaused during development because of insufficient curing of the resin.This phenomenon was probably caused by low polymerization reactivity ofthe epoxy resin having a dicyclopentadiene skeleton due to a smallnumber of functional groups.

The inventors of the present invention have conducted intensive studiesfor solving the problems described above, and have found a compositionsatisfying low water absorption property and high polymerizationreactivity at the same time.

The present invention relates to an epoxy resin composition, including:an epoxy resin (A) represented by Formula (1); an epoxy resin (B) havingan epoxy equivalent of 220 or less and having twice or more epoxy groupsin a molecule than epoxy groups of the epoxy resin (A); and aphotocationic polymerization initiator (C), in which: the epoxy resins(A) and (B) constitute main components; and a weight of the epoxy resin(A) is 40% or more and a weight of the epoxy resin (B) is 30% or morewith respect to a total weight of the epoxy resins (A) and (B).

Further, the present invention relates to a liquid discharge head,including: an energy generating element for generating energy to be usedfor discharge of a liquid; a discharge port for discharging the liquid;and a passage for supplying the liquid to the discharge port, in which:the discharge port and the passage are each formed of a photosensitiveresin. The photosensitive resin is formed of the epoxy resin compositionincluding: an epoxy resin (A) represented by Formula (1); an epoxy resin(B) having an epoxy equivalent of 220 or less and having twice or moreepoxy groups in a molecule than epoxy groups of the epoxy resin (A); anda photocationic polymerization initiator (C), in which: the epoxy resins(A) and (B) constitute main components of the photosensitive resin; anda weight of the epoxy resin (A) is 40% or more and a weight of the epoxyresin (B) is 30% or more with respect to a total weight of the epoxyresins (A) and (B).

Further, the present invention relates to a method of producing a liquiddischarge head, including the steps of: laminating a photosensitiveresin on a substrate having an energy generating element for generatingenergy to be used for discharge of a liquid; and forming a dischargeport for discharging a liquid through exposure and development of thephotosensitive resin and a liquid passage for supplying the liquid tothe discharge port, in which the photosensitive resin is formed of anepoxy resin composition including: an epoxy resin (A) represented byFormula (1); an epoxy resin (B) having an epoxy equivalent of 220 orless and having twice or more epoxy groups in a molecule than epoxygroups of the epoxy resin (A); and a photocationic polymerizationinitiator (C), in which: epoxy resins (A) and (B) constitute maincomponents of the epoxy resin composition; and a weight of the epoxyresin (A) is 40% or more and a weight of the epoxy resin (B) is 30% ormore with respect to a total weight of the epoxy resins (A) and (B).

That is, the present invention is capable of solving the above-mentionedproblems by adding to the epoxy resin (A), an epoxy resin having highpolymerization reactivity providing a final cured product with a highcrosslinking density and capable of maintaining low water absorptionproperty of the epoxy resin (A).

As described above, the photocationic polymerizable epoxy resin of thepresent invention can realize an epoxy resin having both polymerizationreactivity and low water absorption property of a cured product bymixing a highly reactive epoxy resin with the epoxy resin (A) having adicyclopentadiene skeleton. The epoxy resin composition of the presentinvention allows formation of a fine pattern through photocationicpolymerization, and a cured product thereof has low water absorptionproperty due to the dicyclopentadiene skeleton, a high crosslinkingdensity due to polymerization reactivity provided, low swellingproperty, and high mechanical strength.

Thus, the epoxy resin composition of the present invention is used in anenvironment in which the epoxy resin composition is constantly incontact with a liquid as an ink jet recording head, and can sufficientlybe applied in fields requiring a fine line and space pattern in aseveral μm order.

Further, the epoxy resin composition of the present invention can beapplied in fields of microprocessing such as a micromachine.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a stereoscopic perspective view of a cured product of an epoxyresin composition of each of Examples of the present invention used forEvaluation 1.

FIG. 2 is a schematic sectional view of a cured product of an epoxyresin composition of each of Comparative Examples of the presentinvention used for Evaluation 1.

FIG. 3 is a perspective view of a cured product of the epoxy resincomposition of each of Comparative Examples of the present inventionused for Evaluation 1.

FIG. 4 is a perspective view of a cured product of an epoxy resincomposition of each of Examples of the present invention used forEvaluation 2.

FIG. 5 is a schematic diagram of an ink jet recording head according toan embodiment of the present invention.

FIG. 6 is a schematic sectional diagram showing an example of a methodof producing an ink jet recording head of each of Examples of thepresent invention.

FIG. 7 is a schematic sectional diagram showing an example of the methodof producing an ink jet recording head of each of Examples of thepresent invention.

FIG. 8 is a schematic sectional diagram showing an example of the methodof producing an ink jet recording head of each of Examples of thepresent invention.

FIG. 9 is a schematic sectional diagram showing an example of the methodof producing an ink jet recording head of each of Examples of thepresent invention.

FIG. 10 is a schematic sectional diagram showing an example of themethod of producing an ink jet recording head of each of Examples of thepresent invention.

FIG. 11 is a schematic sectional diagram showing an example of themethod of producing an ink jet recording head of each of Examples of thepresent invention.

DESCRIPTION OF THE EMBODIMENTS

Specific examples of an epoxy resin (A) of the present inventionrepresented by Formula (1) and having a dicyclopentadiene skeletoninclude compounds represented by Formulae (7) and (8) described below:

where; R represents a hydrogen atom, a methyl group, an ethyl group, apropyl group, or a t-butyl group; n represents an integer of 0 to 4; andm represents an integer of 1 to 3.

Such an epoxy resin can be produced through a glycidylation reaction ofa polymer of phenol and dicyclopentadiene with epichlorohydrin or thelike. Commercially available examples thereof include HP-7200 series,available from Dainippon Ink and Chemicals, Inc. Such epoxy resins eachhaving an epoxy equivalent of 245 to 280 are known.

The epoxy resin composition of the present invention includes as maincomponents: an epoxy resin represented by Formula (1) as an epoxy resin(A); and an epoxy resin having an epoxy equivalent of 220 or less andhaving twice or more epoxy groups in a molecule than epoxy groups of theepoxy resin (A) as an epoxy resin (B). The main components used hereinrefer to components accounting for 50 wt % or more of a total weight ofthe epoxy resin composition.

The epoxy resin (B) is introduced for enhancing cationic polymerizationreactivity of an entire resin. The inventors of the present inventionhave found that the number of functional groups of the epoxy resin (B)is important for obtaining the above-mentioned effects. That is, theabove-mentioned effects can be obtained by increasing the number ofactive sites contributing to a polymerization reaction. As a result ofdetailed studies, the inventors of the present invention have found thatsignificant effects can be obtained in the case where the epoxy resin(B) has twice or more epoxy groups in a molecule than epoxy groups ofthe epoxy resin (A).

However, property of having a large number of functional groups in amolecule alone can be realized with an epoxy resin having a largemolecular weight and a bulky main chain, and having many repeatingunits. However, use of such a resin provides insufficient number offunctional groups per molecular weight even though the molecular weightof the entire resin composition is high, and thus a cured product maynot have a sufficient crosslinking density.

The inventors of the present invention have studied and found that theepoxy resin (B) must have a sufficiently small number of epoxy groupswith respect to the total molecular weight, that is, epoxy equivalent ofthe epoxy resin (B) compared with that of the epoxy resin (A). To bespecific, the inventors of the present invention have found that theepoxy equivalent of the epoxy resin (B) is preferably 220 or less.

A preferred example of such an epoxy resin is a polyfunctional epoxyresin represented by Formula (2) and having an oxycyclohexane structure.Such a resin having an epoxy equivalent of about 150 to 200 is known:

where: R_(α) represents a k-valent organic compound residue; b1, b2, bk,and so on are each an integer of 1 or more and 100 or less, and a sum ofb1, b2, bk, and so on is no more than 100; k represents an integer of 1or more and 100 or less; A represents an oxycyclohexane skeletonrepresented by Formula (3) or (4) described below: where, X representsan epoxy group.

Further, an epoxy resin represented by Formula (5) may preferably beused.

A specific example of such an epoxy resin is a compound represented byFormula (9). Such an epoxy resin having an epoxy equivalent of about 215is known:

where: R_(β) represents a hydrocarbon compound having an epoxy group;and 1 represents a natural number.

Such an epoxy resin has a large number of epoxy groups per the molecularweight and thus has high cationic polymerization reactivity.Introduction of such an epoxy resin can increase polymerizationreactivity of the entire resin composition and enhance a crosslinkingdensity of a cured product.

Examples of the epoxy resin having the above-mentioned propertiesinclude: EPON SU-8, which is a polyfunctional novolac-type epoxy resinavailable from Shell Chemicals, Ltd.; and EHPE 3150, which is apolyfunctional alicyclic epoxy resin available from Daicel ChemicalIndustries, Ltd. In order to exhibit properties of the two epoxy resinsfully, the weight of the epoxy resin (A) must be 40% or more and theweight of the epoxy resin (B) must be 30% or more with respect to thetotal weight of the epoxy resin (A) and the epoxy resin (B).

Another constituent feature of the epoxy resin composition of thepresent invention is a cationic polymerization initiator (C) such as anaromatic iodonium salt or an aromatic sulfonium salt. Examples ofso-called aromatic onium salts include: SP-150, SP-170, and SP-172(trade names) available from Adeka Corporation; and Rhodorsil 2074(trade name) available from Rhodia Silicones.

Such a photocationic polymerization initiator is capable of generatingcations under UV irradiation and starting polymerization. Thephotocationic polymerization initiator is preferably used in an amountof 0.5 to 10 mass % with respect to 100 mass % of the epoxy resincomponents in the resin composition.

Further, the resin composition may contain additives and the like addedarbitrary as required. For example, a flexibilizer may be added forreducing modulus of a cured product, or a silane coupling agent may beadded for providing enhanced adhesion with a substrate. An additionamount thereof may arbitrarily be set to an amount sufficient fordeveloping a target effect.

EXAMPLES

Hereinafter, the present invention will be described specifically by wayof examples, comparative examples, and production examples. However, thepresent invention is not limited to the examples. The obtained epoxyresin composition was evaluated by the following tests. Note that theterm “parts” used in the examples and the comparative examples refer to“parts by weight” and “wt %” with respect to the total weight of theepoxy resin composition.

In the following description, components having the same function arerepresented by the same number in figures, and description of thecomponent may be omitted.

(Evaluation 1)

The inventors of the present invention have conducted evaluation ofpatterning property by forming the following epoxy resin compositionlayers of Examples and Comparative Examples on substrates, andconducting exposure and development.

Example 1

An epoxy resin composition of Example 1 of the present inventionconsists of the following compositions.

Epoxy resin (A): HP-7200H (manufactured by 66.5 parts Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (epoxy equivalent 28.5 partsof about 180) (manufactured by Daicel Chemical Industries, Ltd.)Photocationic polymerization initiator: SP-172  1.5 parts (manufacturedby Adeka Corporation) Additive (silane coupling agent): A-187  3.5 parts(manufactured by Nihonunika Corporation)

The epoxy resin composition of Example 1 was dissolved in methylisobutyl ketone to obtain an epoxy resin solution. In addition, theepoxy resin compositions of Examples 2 to 4 and Comparative Examples 1and 2 described below were each performed in the same manner as Example1 to obtain an epoxy resin solution.

Example 2

Epoxy resin (A): HP-7200 (manufactured by 66.5 parts Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (manufactured by 28.5 partsDaicel Chemical Industries, Ltd.) Photocationic polymerizationinitiator: SP-172  1.5 parts (manufactured by Adeka Corporation)Additive (silane coupling agent): A-187  3.5 parts (manufactured byNihonunika Corporation)

Example 3

Epoxy resin (A): HP-7200H (manufactured by  57 parts Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (manufactured by  38 partsDaicel Chemical Industries, Ltd.) Photocationic polymerizationinitiator: SP-172 1.5 parts (manufactured by Adeka Corporation) Additive(silane coupling agent): A-187 3.5 parts (manufactured by NihonunikaCorporation)

Example 4

Epoxy resin (A): HP-7200 (manufactured by  57 parts Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (manufactured by  38 partsDaicel Chemical Industries, Ltd.) Photocationic polymerizationinitiator: SP-172 1.5 parts (manufactured by Adeka Corporation) Additive(silane coupling agent): A-187 3.5 parts (manufactured by NihonunikaCorporation)

Example 5

Epoxy resin (A): HP-7200H (manufactured by 47.5 parts Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (manufactured by 47.5 partsDaicel Chemical Industries, Ltd.) Photocationic polymerizationinitiator: SP-172  1.5 parts (manufactured by Adeka Corporation)Additive (silane coupling agent): A-187  3.5 parts (manufactured byNihonunika Corporation)

Example 6

Epoxy resin (A): HP-7200 (manufactured by 47.5 parts Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (manufactured by 47.5 partsDaicel Chemical Industries, Ltd.) Photocationic polymerizationinitiator: SP-172  1.5 parts (manufactured by Adeka Corporation)Additive (silane coupling agent): A-187  3.5 parts (manufactured byNihonunika Corporation)

Example 7

Epoxy resin (A): HP-7200H (manufactured by  38 parts Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (manufactured by  57 partsDaicel Chemical Industries, Ltd.) Photocationic polymerizationinitiator: SP-172 1.5 parts (manufactured by Adeka Corporation) Additive(silane coupling agent): A-187 3.5 parts (manufactured by NihonunikaCorporation)

Example 8

Epoxy resin (A): HP-7200 (manufactured by  38 parts Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (manufactured by  57 partsDaicel Chemical Industries, Ltd.) Photocationic polymerizationinitiator: SP-172 1.5 parts (manufactured by Adeka Corporation) Additive(silane coupling agent): A-187 3.5 parts (manufactured by NihonunikaCorporation)

Comparative Example 1

Epoxy resin (A): HP-7200H (manufactured by  95 parts Dainippon Ink andChemicals, Inc.) Photocationic polymerization initiator: SP-172 1.5parts (manufactured by Adeka Corporation) Additive (silane couplingagent): A-187 3.5 parts (manufactured by Nihonunika Corporation)

Comparative Example 2

Epoxy resin (A): HP-7200 (manufactured by  95 parts Dainippon Ink andChemicals, Inc.) Photocationic polymerization initiator: SP-172 1.5parts (manufactured by Adeka Corporation) Additive (silane couplingagent): A-187 3.5 parts (manufactured by Nihonunika Corporation)

Comparative Example 3

Epoxy resin (A): HP-7200 (manufactured by 85.5 parts  Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (manufactured by 9.5 partsDaicel Chemical Industries, Ltd.) Photocationic polymerizationinitiator: SP-172 1.5 parts (manufactured by Adeka Corporation) Additive(silane coupling agent): A-187 3.5 parts (manufactured by NihonunikaCorporation)

Comparative Example 4

Epoxy resin (A): HP-7200 (manufactured by 85.5 parts  Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (manufactured by 9.5 partsDaicel Chemical Industries, Ltd.) Photocationic polymerizationinitiator: SP-172 1.5 parts (manufactured by Adeka Corporation) Additive(silane coupling agent): A-187 3.5 parts (manufactured by NihonunikaCorporation)

Comparative Example 5

Epoxy resin (A): HP-7200H (manufactured by  76 parts Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (manufactured by  19 partsDaicel Chemical Industries, Ltd.) Photocationic polymerizationinitiator: SP-172 1.5 parts (manufactured by Adeka Corporation) Additive(silane coupling agent): A-187 3.5 parts (manufactured by NihonunikaCorporation)

Comparative Example 6

Epoxy resin (A): HP-7200 (manufactured by  76 parts Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (manufactured by  19 partsDaicel Chemical Industries, Ltd.) Photocationic polymerizationinitiator: SP-172 1.5 parts (manufactured by Adeka Corporation) Additive(silane coupling agent): A-187 3.5 parts (manufactured by NihonunikaCorporation)

First, a 6-inch Si wafer was prepared as a substrate, and an SiO₂ layerhaving a thickness of 1.0 μm was formed through thermal oxidation. Next,an epoxy resin solution employing the epoxy resin composition of each ofExamples 1 to 8 and Comparative Examples 1 and 6 was formed into a filmon the substrate by a spin coating method, and the film was baked at 90°C. for 5 min for evaporation of an application solvent, to therebyobtain a resin composition layer having a thickness of 20 μm.

Then, the resin composition layer on the substrate was patterned (a lineand space pattern of 50 μm in length and 10 μm in width) at an exposureof 1,000 mJ/cm² by using a mask aligner MPA600 (trade name) manufacturedby Canon Inc.

After exposure, the resin composition layer was heated at 90° C. for 4min on a hot plate, developed with a methyl isobutyl ketone/xylene mixedsolvent, and cured through heat treatment at 200° C. for 1 hour forpatterning.

FIG. 1 is a stereoscopic perspective view of a pattern 16 employing theepoxy resin composition of each of Examples 1 to 8 used forEvaluation 1. FIG. 2 is a sectional view of a pattern employing theepoxy resin composition of each of Comparative Examples 1 and 6 used forEvaluation 1. FIG. 3 is an enlarged perspective view of a circled partof FIG. 2.

As shown in FIG. 1, observation of the pattern after curing revealedthat: the pattern employing the epoxy resin composition of each ofExamples 1 to 8 had a sharp edge portion 11; and a line and spacepattern satisfying a level to be applied to a passage forming member ofan ink jet recording head was obtained. Reference numeral 12 representsa space in the pattern.

However, the pattern formed by using the epoxy resin composition of eachof Comparative Examples 1 to 6 had a blunt edge part 11 as shown in FIG.2. To be specific, as shown in FIG. 3, the edge part 11 was rounded andhad a shape projecting to a space part compared with surrounding parts.

The observation of a line and space width revealed that: the curedproducts according to Examples of the present invention hadsubstantially uniform dimensions; and the cured products according toComparative Examples had varying space dimensions compared to those ofExamples of the present invention. This phenomenon was probably causedby low photopolymerization reactivity of the resin A and a lowcrosslinking density of the pattern in a vicinity of the edge comparedwith those of other parts.

As described above, the results confirmed that fine photopatterning canbe conducted with the resin composition having an amount ratio of theresin (A) to the resin (B) of (A):(B)=4:6 to 7:3, that is, the resincomposition containing 30% or more of the resin (A) and 40% or more ofthe resin (B) with respect to the total amount of the resins (A) and(B).

(Evaluation 2)

Next, epoxy resin compositions according to the following examples areprepared.

Example 9

An epoxy resin composition of Example 9 of the present inventionconsists of the following compositions.

Epoxy resin (A): HP-7200 (manufactured by 28.5 parts Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (epoxy equivalent 28.5 partsof about 180) (manufactured by Daicel Chemical Industries, Ltd.)Bis-phenol A type epoxy resin: EP-5100-75X (epoxy  38 parts equivalentof about 630, manufactured by Adeka Corporation) Photocationicpolymerization initiator: SP-172  1.5 parts (manufactured by AdekaCorporation) Additive (silane coupling agent): A-187  3.5 parts(manufactured by Nihonunika Corporation)

Example 10

An epoxy resin composition of Example 10 of the present inventionconsists of the following compositions.

Epoxy resin (A): HP-7200 (manufactured by 23.75 parts Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (epoxy equivalent 23.75parts of about 180) (manufactured by Daicel Chemical Industries, Ltd.)Bis-phenol A type epoxy resin: EP-5100-75X (epoxy 47.5 parts equivalentof about 630, manufactured by Adeka Corporation) Photocationicpolymerization initiator: SP-172  1.5 parts (manufactured by AdekaCorporation) Additive (silane coupling agent): A-187  3.5 parts(manufactured by Nihonunika Corporation)

Comparative Example 7

An epoxy resin composition of Example 7 of the present inventionconsists of the following compositions.

Epoxy resin (A): HP-7200 (manufactured by 19 parts Dainippon Ink andChemicals, Inc.) Epoxy resin (B): EHPE 3150 (epoxy equivalent 19 partsof about 180) (manufactured by Daicel Chemical Industries, Ltd.)Bis-phenol A type epoxy resin: EP-5100-75X (epoxy 57 parts equivalent ofabout 630, manufactured by Adeka Corporation) Photocationicpolymerization initiator: SP-172 1.5 parts  (manufactured by AdekaCorporation) Additive (silane coupling agent): A-187 3.5 parts (manufactured by Nihonunika Corporation)

These examples and the resin compositions of examples 1 to 8 wasdissolved in methyl isobutyl ketone and then a film of the resincomposition is formed on the substrate by spin coating method, and thefilm was baked at 90° C. for 5 min for evaporation of an applicationsolvent, to thereby obtain a resin composition layer having a thicknessof 20 μm.

Then, a predetermined region of the resin composition layer was curedand patterned (a pattern in which two lines of a hole pattern having adiameter of 6 μm was formed at a 40 μm pitch on a pattern of 15 mm inlength and 0.6 mm in width) by using a mask aligner MPA600 (trade name)manufactured by Canon Inc.

By Observing the produced patterns, in the pattern according to theresin composition of the comparative example 7, the entire edge portionof the cured resin is peeled from the substrate. On the contrary, in thepatterns according to the epoxy resin compositions of examples 9 and 10,peeling was remarkably reduced and had durability for use as an ink jetrecording head. This is because the epoxy resin composition ofcomparative example 7 has larger ratio of Bis-phenol A type epoxy resinhaving high epoxy equivalent as compared with the examples 9 and 10 hasless number of functional groups relating chemical adhesiveness.

In addition, in the patterns using the resin compositions according toexamples 1 to 8 peeling from the substrate was not observed.

As mentioned above, according to the present invention, it is preferablethat a ratio of the resin (A) and the resin (B) to whole weight of theepoxy resin composition is at least no less than 50 weight percent.

(Evaluation 3)

Patterning property of the epoxy resin composition of each of Examples 1to 8, in which a favorable line and space pattern was obtained inEvaluation 1, was evaluated under conditions similar to those of apassage forming member of an ink jet recording head as a specificapplication example.

First, a 6-inch Si wafer was prepared as a substrate, and an SiO₂ layerhaving a thickness of 1.0 μm was formed through thermal oxidation.

Next, an epoxy resin solution containing the epoxy resin composition ofeach of Examples dissolved in methyl isobutyl ketone was formed into afilm on the substrate by spin coating, and the film was baked at 90° C.for 5 min for evaporation of an application solvent, to thereby obtain aresin composition layer having a thickness of 20 μm.

Then, the resin composition layer was patterned (a pattern in which twolines of a hole pattern having a diameter of 15 μm was formed at a 40 μmpitch on a pattern of 30 mm in length and 0.6 mm in width) by using amask aligner MPA600 (trade name) manufactured by Canon Inc. The exposurewas changed within a range of 300 to 1,000 mJ/cm², and a plurality ofresin composition layers subjected to different exposure but notdeveloped were obtained for the epoxy resin composition of each ofExamples. Then, the resin composition layer was heated on a hot plate,developed, and cured through heat treatment, to thereby obtain a patternas shown in FIG. 4. Note that heating conditions and the like werearbitrarily adjusted.

As described above, a plurality of cured products 13 were obtained foreach of Examples.

Observation of each of the cured products on a surface having a holepattern 14 formed revealed that a favorable pattern with a sharp edgepart was obtained. Cracks on an opened surface of the hole were visuallyobserved. Evaluation criteria are as follows.

A: No noticeable cracks were observed in any cured products.

B: Noticeable cracks were observed in part of cured products.

Table 1 shows the results.

TABLE 1 Evaluation of epoxy resin composition Observation of cracksExample 1 B Example 2 B Example 3 B Example 4 B Example 5 A Example 6 AExample 7 A Example 8 A

In view of suppressing cracks, the results indicated that the epoxyresin composition of each of Examples 5 to 8, that is, the epoxy resincomposition satisfying [epoxy resin (B) (parts by weight)/epoxy resin(A) (parts by weight)]≧1 was particularly preferred.

The evaluation described above revealed that the epoxy resin compositionof the present invention had sufficient polymerization reactivity forforming a fine pattern and can be applied to an ink jet recording head.

Next, evaluation was conducted on water absorption property of a passagewall forming member of an ink jet recording head produced by using theepoxy resin composition of the present invention.

(Evaluation 4)

First, an ink jet recording head to which the present invention can beapplied will be described.

FIG. 6 is a schematic diagram showing an ink jet recording headaccording to an embodiment of the present invention.

The ink jet recording head according to the embodiment of the presentinvention includes a substrate 1 having two lines of energy generatingelements 2 to be used for discharging ink formed at a predeterminedpitch. The substrate 1 has a supply port 10 for supplying ink openedbetween the energy generating elements. On the substrate 1, an inkdischarge port 9 opened toward each of the energy generating elementsand an ink passage connected from the ink supply port 10 to each of theink discharge port 9 are formed with an ink passage wall forming member.

The ink jet recording head is arranged such that a surface having theink discharge port 10 formed faces a recording surface of a recordingmedium. In the ink jet recording head, a pressure generated by theenergy generating element 2 is applied to ink filled in the ink passagethrough the ink supply port 10 to discharge ink droplets from the inkdischarge port 9, and the ink droplets are attached to the recordingmedium for recording.

The ink jet recording head may be loaded in device such as a printer, acopying machine, a facsimile, a word processor having a printer part,and an industrial recording device combined with various processingdevices.

Next, a method of producing the ink jet recording head according to theembodiment of the present invention will be described with reference tothe figures. Note that FIGS. 6, 7, 8, 9, 10 and 11 to be used in thefollowing description show sectional views of FIG. 5 at the positiona-a′.

First, on the substrate 1 provided with a mask 3 for forming an inksupply port on a back surface, an electric-heat exchange element as theenergy generating element 2 for discharging ink was arranged, andprotective layers 4 and 5 were formed (FIG. 6). Note that the energygenerating element 2 is connected with a control signal input electrode(not shown) for activating the element.

Then, an adhesive layer 6 was formed on the substrate 1 (FIG. 7).

Then, a solution containing a positive photosensitive resin dissolved ina solvent was applied to the substrate 1, to thereby form a layer havinga thickness of 12 μm. Exposure was conducted by using UX3000manufactured by Ushio Inc., and development was conducted by usingmethyl isobutyl ketone, to thereby form an ink passage pattern 7 (FIG.8).

Next, the epoxy resin composition of each of Examples of the presentinvention was dissolved in methyl isobutyl ketone, and a coated resinlayer 8 was formed on the ink passage pattern 7. The whole was prebakedat 90° C. for 4 min (FIG. 9).

Next, exposure was conducted by using a liquid discharge port maskpattern by using a mask aligner MPA-600 Super manufactured by CanonInc., and development was conducted by using methyl isobutyl ketone, tothereby form a very small discharge port 9 (ink discharge port: diameterof 8 μm) (FIG. 10).

Then, the back surface of the substrate 1 was etched by Si anisotropicetching to form the ink supply port 10 and remove the protective layersand the ink passage pattern 7 on the ink supply port 10, For completecuring of the resin composition forming the coated resin layer 8 servingas an ink passage wall, a passage wall forming member was formed underheating at 200° C. for 1 hour, to thereby obtain an ink jet recordinghead (FIG. 11).

The ink jet recording head employing the passage wall forming memberformed of the cured product of the epoxy resin composition of each ofExamples 1 to 8 of the present invention was produced by the productionmethod described above.

Next, the produced ink jet recording head was loaded in a recordingdevice, and 10,000-page test print was conducted with high alkali ink byusing ink BCI-6C available from Canon Inc. As a result, no image wasdistorted.

The diameter of the discharge port after the test print was comparedwith that immediately after production, and a reduction ratio wasmeasured. The reduction ratio of the ink jet recording head according toeach of Examples 1 to 8 of the present invention was 5% at maximum. Theresults confirmed that the ink jet recording head according to each ofExamples 1 to 8 of the present invention maintained ink resistantproperty comparable to that of the conventionally known ink jetrecording head.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2005-363453, filed Dec. 16, 2005, which is hereby incorporated byreference herein in its entirety.

1. A liquid discharge head, comprising: a substrate provided with anenergy generating element for generating energy to be used fordischarging liquid from a discharge port corresponding to the energygenerating element; a passage wall member provided with a wall ofpassage of liquid communicated with the discharge port, provided on thesubstrate, wherein the passage wall member is a cured product ofphotosensitive resin comprising: an epoxy resin (A) represented byFormula (1); an epoxy resin (B) having an epoxy equivalent of 220 orless and having twice or more epoxy groups in a molecule than epoxygroups of the epoxy resin (A); and a photocationic polymerizationinitiator (C), wherein: the epoxy resins (A) and (B) constitute maincomponents of the photosensitive resin; and a weight of the epoxy resin(A) is 40% or more and a weight of the epoxy resin (B) is 30% or morewith respect to a total weight of the epoxy resins (A) and (B):

where: R represents a hydrogen atom, a methyl group, an ethyl group, apropyl group, or a t-butyl group; n represents an integer of 0 or moreand 4 or less; and m represents an integer of 1 or more and 3 or less.2. A liquid discharge head according to claim 1, wherein the epoxy resin(B) comprises an epoxy resin represented by Formula (2) described below:

where: R_(α) represents a k-valent organic compound residue; b1, b2, bk,and so on are each an integer of 1 or more and 100 or less, and a sum ofb1, b2, bk, and so on is 100;k represents an integer of 1 or more and100 or less; and A represents a skeleton represented by Formula (3) or(4) described below:

where X represents an epoxy group.
 3. A liquid discharge head accordingto claim 1, wherein the epoxy resin (B) comprises an epoxy resinrepresented by Formula (5) described below:

where: R_(β) represents a hydrocarbon compound having an epoxy group;and 1 represents a natural number.
 4. A liquid discharge head accordingto claim 1, wherein the photocationic polymerization initiator is anaromatic sulfonium salt or an aromatic iodonium salt.
 5. A liquiddischarge head according to claim 4, wherein the aromatic sulfonium saltis a compound represented by Formula (6) described below.


6. A liquid discharge head, comprising: a substrate provided with anenergy generating element for generating energy to be used fordischarging liquid from a discharge port member provided with adischarge port corresponding to the energy generating element, whereinthe discharge port member is a cured product of a photosensitive resincomprising: an epoxy resin (A) represented by Formula (1); an epoxyresin (B) having an epoxy equivalent of 220 or less and having twice ormore epoxy groups in a molecule than epoxy groups of the epoxy resin(A); and a photocationic polymerization initiator (C), wherein: theepoxy resins (A) and (B) constitute main components of thephotosensitive resin; and a weight of the epoxy resin (A) is 40% or moreand a weight of the epoxy resin (B) is 30% or more with respect to atotal weight of the epoxy resins (A) and (B):

where: R represents a hydrogen atom, a methyl group, an ethyl group, apropyl group, or a t-butyl group; n represents an integer of 0 or moreand 4 or less; and m represents an integer of 1 or more and 3 or less.7. A liquid discharge head according to claim 6, wherein the epoxy resin(B) comprises an epoxy resin represented by Formula (2) described below:

where: R_(α) represents a k-valent organic compound residue; b1, b2, bk,and so on are each an integer of 1 or more and 100 or less, and a sum ofb1, b2, bk, and so on is 100; k represents an integer of 1 or more and100 or less; and A represents a skeleton represented by Formula (3) or(4) described below:

where X represents an epoxy group.
 8. A liquid discharge head accordingto claim 6, wherein the epoxy resin (B) comprises an epoxy resinrepresented by Formula (5) described below:

where: R_(β) represents a hydrocarbon compound having an epoxy group;and 1 represents a natural number.
 9. A liquid discharge head accordingto claim 6, wherein the cationic polymerization initiator is an aromaticsulfonium salt or an aromatic iodonium salt.
 10. A liquid discharge headaccording to claim 9, wherein the aromatic sulfonium salt is a compoundrepresented by Formula (6) described below.